Methanol Synthesis from Biogas: Thermodynamics, Computer Simulation, and Economic Evaluation

Hardiman, Kelfin (2001). Methanol Synthesis from Biogas: Thermodynamics, Computer Simulation, and Economic Evaluation Honours Thesis, School of Engineering, The University of Queensland.

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Author Hardiman, Kelfin
Thesis Title Methanol Synthesis from Biogas: Thermodynamics, Computer Simulation, and Economic Evaluation
School, Centre or Institute School of Engineering
Institution The University of Queensland
Publication date 2001
Thesis type Honours Thesis
Supervisor G. Q. (Max) Lu
Abdulhamid M. Dajan
Total pages 108
Language eng
Subjects 0904 Chemical Engineering
Formatted abstract
The production of synthesis gas (CO+H2) from biogas (CH4+CO2) via carbon dioxide reforming reaction has started to attract the attentions of many industries and researches. This process utilises CO2, a major greenhouse gas, and produces synthesis gas with a more ideal H2/CO molar ratio, which is suitable for the methanol synthesis. Unfortunately, carbon dioxide reforming technology is not widely employed in the industry, yet due to major problems associated with carbon formation.

A thermodynamics analysis was carried out by calculating the enthalpy changes, 0 DHT , and Gibbs free-energy changes, 0T DG of all the reactions involved in the production of synthesis gas and the synthesis of methanol. The enthalpy changes calculation allows us to discover that carbon dioxide reforming, reverse water-gas shift and methane cracking reactions are favoured by high temperatures. On the other hand, low temperatures favour carbon deposition and methanol synthesis reactions. The Gibbs free-energy change was calculated to determine the thermodynamic feasibility of these reactions at a specific temperature range and their equilibrium positions in terms of temperature. The calculations followed the approach used in Smith and Van Ness [10]. Then, CHEMEQ, which is a computer program developed by Sandler [7], was used to confirm the calculations.

SuperPro Designer computer software was used to simulate the performance of various methanol synthesis systems. These are;

1. Without recycle;
2. With recycle input after reactor R-1;
3. With recycle before reactor R-1;
4. With a duplicate system of reactors (R-1 + R-1¢).

It was found that theoretically System 3 is the most optimum. In the simulation, we assumed that there are no side reactions, and the catalysts used in synthesis gas reactor (R-1) and methanol producing reactor (R-2) are Ni/g-Al2O3 and CuO/ZnO/AlO3 respectively. The simulation shows that an operating R-1 temperature of at least 650°C is required in order to produce a good methanol yield regardless of the system type. In addition, it was found that the best operating R-2 pressure for Systems 2 & 3 are 200 atm and 50 atm respectively. Furthermore, the most ideal CO/H2 molar ratio of gas flow entering R-2 was around 7:13.
Keyword Methanol Synthesis

Document type: Thesis
Collection: UQ Theses (non-RHD) - UQ staff and students only
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Created: Thu, 08 Jan 2015, 12:36:53 EST by Asma Asrar Qureshi on behalf of Scholarly Communication and Digitisation Service